The overall objective of the Human Subjects and Statistical Analysis Core Unit (Core C) is to provide support services that will improve the quality, the productivity, and cost effectiveness of the human subjects research, including the provision of needed cohort maintenance services, data entry and management services, and advanced statistical expertise to investigators. The primary functions of this research core are divided into five major categories: (l) design and refinement of human subjects research studies and assessment protocols, incorporating recent advances in longitudinal research techniques and building upon the collective and diverse expertise of the Center's investigators; (2) subject recruitment and retention (cohort maintenance) support services for Center investigators; (3) data management services, ranging from assistance with data entry and editing, file set-up, file maintenance and mergers to master archiving of databases; (4) statistical analyses of multivariate and longitudinal databases, especially the application of sophisticated data analytic strategies and facilitation of cross-study and meta- analytic analyses; and (5) seminars and training in advanced statistical techniques, new software statistical and graphics packages, and promising opportunities for post hoc and cross-study data analyses on questions relevant to the Center's theme.